1. Field of the Invention
The present invention relates to a loudspeaker having a magnesium-lithium alloy cone and the method of manufacturing the cone by making use of the characteristics and manufacturability of the magnesium-lithium alloy to make a cone of the loudspeaker having high rigidity and moderate internal loss characteristics. The present invention also provides an excellent manufacturability used for the lightweight and high-fidelity loudspeaker cone.
2. Description of the Prior Art
In general, a conventional prior art loudspeaker comprises: a frame structure, having an expanded opening in its front end and a magnetic element at its rear end; a voice coil, disposed in the middle of the magnetic element; a damper, adhering to the voice coil; a cone, disposed on the internal diameter of the expanded opening of the frame structure and adhering to the voice coil; since the appearance is restricted by the limited space, the cones of earlier stage were made of paper, and then polypropylene products gradually showed up. Aluminum metal is used for making cones now.
Two factors have been taken into consideration for selecting the material for making the cone: (1) Rigidity and (2) Internal loss . In mechanical physics, the larger the rigidity of the material, the higher is the relative natural resonant frequency. Therefore, the application of the cone of the loudspeaker in a higher audio frequency will cause distortion to the sound due to the splitting motion of the resonance, and thus giving a wider effective frequency range. For the material with good internal loss, the internal resistance of the material can absorb and eliminate the energy of the resonance quickly. The application of the cone of the loudspeaker with an appropriate internal resistance can obtain a plane sound pressure curve and a more beautiful metal color in the effective frequency range.
At present, most of the materials used in the prior art loudspeakers are unable to take care of both characteristics of the rigidity and the internal loss. For example, although the paper cone of the loudspeaker has excellent internal loss, but its rigidity is not good, such that the effective frequency range is restricted. In practice, paper products require quite a few thickness to be formed; in addition to the limitation on its bulky appearance, the paper product will be moistened and damaged by fungi easily.
Although the aluminum product with better rigidity does not have such shortcoming, the cone made of aluminum metal is a poorer internal loss than the cone made of paper and polypropylene, and thus causing significant distortion to the sound due to the split motion of the resonance in a higher frequency range.
Recently, magnesium alloy is used to make the case of notebook computers due to its characteristics for light weight, high rigidity, good heat dissipation, absorbing electromagnetic wave and capable for being recycled. Therefore, related manufacturers generally accept the magnesium alloy and use it for mass production. The loudspeaker manufacturers also follow and intend to apply magnesium alloy on the cone of the loudspeaker, but the die-casting process has limitation on the thickness of the finished products. Magnesium alloy cannot be used for developing cones of the loudspeaker, since the stamping process of the magnesium alloy sheet is not suitable for such production. It is unable to manufacture and produce the cone under normal temperature because the crystalline grain of magnesium alloy is a Hexagonal Close Pack (HCP) crystal lattice structure and has the poor extendability of the material. It requires high temperature for the manufacturability, and thus relatively increases the cost and endangers the safety of the manufacturing.
In view of the shortcomings of the cone of the prior art loudspeaker, the inventor of the present invention based on years of experience in the related industry conducted extensive research to resolve the aforementioned problem and invented the present invention made of a material having good rigidity and internal loss, providing excellent manufacturability under normal temperature for stamping and forming the cone of loudspeakers.
The primary objective of the present invention is to provide a material having excellent rigidity and internal loss characteristics as well as easy manufacturability with metal appearance. Such material is applied on the development of the cone of the high-fidelity loudspeaker and to overcome the shortcomings of the prior art material that is unable to take care of both the rigidity and internal loss.
To accomplish the foregoing objectives, the loudspeaker having a magnesium-lithium alloy cone of the present invention comprises a frame structure, having an expanded opening in its front end and a magnetic element at its rear end; a voice coil, disposed in the middle of the magnetic element; a damper, adhering to the voice coil; a cone, disposed on the internal diameter of the expanded opening of the frame structure and adhering to the voice coil; characterized in that the cone of the loudspeaker is formed by stamping the magnesium-lithium alloy under normal temperature, and the characteristics of the magnesium-lithium alloy material and the stamping process to produce the cone of the loudspeaker, which gives a better and a planer sound pressure curve, a wider effective bandwidth, and a more beautiful metal color than the cone of the prior art loudspeaker within the audible frequency range.